The attached sample add-in exposes an example of handling a fully functional ClientFeature including the following functionalities:
Creation through InteractionEvents, edit, double-clicked event, associated ClientGraphics.
I wrote this add-in upon request for a customer, so it is very specific to their workflow. It helps quickly creating an extrusion based on the selected edge(s), the resulting shape makes think about a dog bone, hence the name of the plug-in.
I believe it might be a good example for programmers looking for creating advanced ClientFeatures.